1. Field of the Invention
The present invention relates to a common-mode choke coil adapted for high current applications and surface-mounting.
2. Description of the Related Art
Generally, in an electrical transmission cable utilizing a differential transmission system and the like, a common mode choke coil is interposed between two signal lines for eliminating common mode noise current caused by a difference between them in transmission characteristics such as a difference in impedance. Such a common-mode choke coil is provided with two sets of choke coils whose windings are wound on a core (magnetic body) in the same direction.
FIGS. 9A and 9B show a conventional common-mode choke coil which includes a core assembly 100 having a ring-shaped core made of magnetic material, with the outer periphery of the core assembly covered with a core cover made of synthetic resin constituting an insulating layer, a first coil 20 of round copper wire wound on a part of the outer periphery of the core assembly, and a second coil 30 of round copper wire wound on another part of the outer periphery of the core assembly in the same direction as the first coil 20.
When such a common-mode choke coil is used for surface-mounting, the coil is required to have a base plate 40 provided with terminals 50 to which the first and second coils 20 and 30 are connected at their respective ends 20a, 30a. 
This has caused a problem that welding the ends 20a, 30a of the first and second coils to the respective terminals 50 and like operations require a considerable workload, thereby leading to increased manufacturing cost.
Also, such a conventional coil has a problem that, as the core assembly 100, on which the first and second coils 20, 30 are wound, is mounted on a circuit board in such a manner that it stands thereon, a design for reduction in height of the circuit board is rendered wasted.
Japanese Patent Laid-Open. No. 2008-244247 discloses a common-mode choke coil of this kind which the Applicant of the present application previously proposed.